This invention relates to baghouse systems, and to methods and systems for detecting the presence of a leak in a bag installed in a baghouse system.
Regulatory controls have become increasingly important as air quality standards and resulting industrial emission permits have become more stringent. Some industrial applications use filters to separate dust and other airborne particulate matter from the air. A baghouse filter is one apparatus used to reduce emissions of particulate matter from industrial sources and improve air quality by filtering dust and other particulate from the air.
A baghouse system is one type of dust collection apparatus that uses filtration media, usually of fabric, forming bags that collect the dust. A baghouse may include a housing separated into two or more chambers or plenums one internal and one external to the bags. In an exemplary baghouse, air enters the baghouse system through “dirty air” chambers internal of the bags and passes through a desired number of tubular fabric sheets, or baghouse bags into the “filtered air” chambers external of the bags. Within each dirty air chamber the bag acts as a filter medium to collect the particulate matter in the air. The baghouse bags are usually made of a fabric material suitable for filtering airborne particulate matter to prevent the passage of particles larger than a specified size, while allowing air to pass through. The effectiveness of the baghouse system may be measured by the opacity of the filtered air exiting the baghouse system.
In operation, dirty air containing dust and other particulate matter from an industrial process enters a “dirty air” chamber and is forced or drawn through the baghouse bags. A fan or blower may be used to force the dirty air into the “dirty air” chamber, or draw air from the “filtered air” chamber of the baghouse system. The particulate matter in the dirty air that is larger than the openings in the filter medium of the bags collects on the surface of the bags on the dirty air side while the filtered air passes through the bags. The resulting filtered air exits the baghouse system through an exhaust duct or stack. A fan or blower forces or draws the dirty air through the baghouse bags and into the filtered air chambers.
In the baghouse system, the bags tend to wear and develop leaks over time. Such leaks degrade the filtering effectiveness of the baghouse system and increase the opacity of the exiting filtered air. A baghouse may include a plurality of bags that will eventually need to be replaced. Such replacement may be performed at scheduled intervals corresponding to a pre-determined expected useful life of the bags. However, some baghouse bags may function beyond their expected life, while others develop leaks and become ineffective before their scheduled life expectancy. Replacing specific bags that develop leaks before the scheduled useful life has been impractical in the past because it is difficult to determine which bag or bags of the baghouse system have developed leaks.
It is desirable to replace or repair such leaking bags as they develop to maintain an efficient and effective baghouse system and maintain the air quality of the exiting air. However, a baghouse system can employ tens, hundreds, or even thousands, of filtration bags at the same time. In the past, a person had to go into the baghouse and visually inspect the bags to find which had developed leaks and whether or not such leaking bags could be repaired or had to be replaced. Such a human visual inspection was very time-consuming and inefficient. Furthermore, visual inspection by a person was inadequate for detecting small leaks in bags because small leaks are, at best difficult to see. Unfortunately, such a small leak may still cause unacceptable performance of the baghouse system and degradation of the air quality.
Various methods have been developed in the past to aid in visual inspection, such as introducing fluorescent powders into the air stream, and inspecting the bags with black light or other lights. While these methods have improved inspection techniques, the effectiveness of such methods was limited and expensive. These methods still relied on the accuracy of visual inspection. What has been needed is a more efficient method and system for detecting leaks in bags of baghouse systems, and a method and system that can detect small leaks and the location of leaks in the baghouse system.
A method is presently disclosed for detecting a leak in a bag installed in a baghouse system, comprising the steps of:                a) positioning a sensor to measure opacity in an outlet of a baghouse system having at least one compartment;        b) measuring opacity of gas flow through the outlet during start-up of one or more compartments in the baghouse system;        c) generating electrical signals corresponding to the opacity measured by the sensor; and        d) comparing the electrical signals corresponding to the opacity measured by the sensor with a reference characteristic of a leak in a bag of the baghouse bag system.        
The reference characteristic of a leak in a bag of the baghouse bag system may be an electrical signal representing opacity measurements from the sensor during the start-up of at least one compartment in the baghouse system with a leak in a bag. Alternately or in addition, the reference characteristic of a leak in a bag in the baghouse bag system may include a predetermined threshold value derived from empirical opacity measurements.
The method of detecting a leak in a bag installed in a baghouse system may comprise the steps of:                a) positioning a light emitting diode in an outlet of a baghouse system having at least one compartment;        b) positioning a sensor to measure light emitted from the light emitting diode to measure opacity in the outlet of a baghouse system;        c) measuring opacity of gas flow through the outlet during start-up of one or more compartments of the baghouse system;        d) generating electrical signals corresponding to the opacity measured by the sensor; and        e) comparing the electrical signals corresponding to the opacity measured by the sensor with electrical signals characteristic of a leak in a bag of the baghouse bag system.        
The method of detecting a leak in a bag installed in a baghouse system may include the steps of starting to acquire opacity measurements from the sensor prior to the start-up of one or more compartments of the baghouse system and comparing the electrical signals corresponding to the opacity measured prior to the start-up with the electrical signals corresponding to the opacity measured by the sensor at least during the start-up to identify the presence of a leak in a bag of the baghouse bag system. Alternately or in addition, the method may include the steps of generating a reference electrical signal representing opacity measurements from the sensor during the start-up of at least one compartment in the baghouse system with a leak in a bag and comparing the electrical signals corresponding to the opacity measured by the sensor with the reference electrical signal to determine when a leak has occurred in a bag of the baghouse system. The method may include the steps of comparing the opacity measured by the sensor to a predetermined threshold value and indicating a detected leak in the baghouse bag if the opacity exceeds the predetermined threshold value.
The method of detecting a leak in a bag installed in a baghouse system may include determining the approximate location of a baghouse bag having a leak in at least one compartment using the time between the start-up of the compartment or compartments and a measured change in opacity by the sensor characteristic of a leak in a bag, and the flow rate of gas between the compartment or compartments starting-up and the sensor.
A system is disclosed for detecting a leak in a bag installed in a baghouse system, comprising:                a) a sensor positioned to measure opacity in an outlet of a baghouse system having at least one compartment; and        b) a processor capable of generating electrical signals corresponding to the opacity measured by the sensor and comparing the electrical signals corresponding to the opacity measured by the sensor with electrical signals characteristic of a leak in a bag of the baghouse bag system.        
Alternately, a system for detecting a leak in a bag installed in a baghouse system may comprise:                a) a light emitting diode positioned in an outlet from a baghouse system having at least one compartment;        b) a sensor positioned to measure light emitted by the light emitting diode to measure the opacity gas flow in an outlet from a baghouse system; and        c) a processor to generate electrical signals corresponding to the opacity measured by the sensor and compare the electrical signals to the opacity measured by the sensor with electrical signals characteristic of a leak in a bag of the baghouse bag system.        
The electrical signals characteristic of a leak may comprise reference electrical signals representing opacity measurements from the sensor during start-up of at least one compartment of the baghouse system with a leak in a bag. The processor may be capable of processing electrical signals before and during start-up of one or more compartments of the baghouse system. Further, the processor may be capable of processing electrical signals corresponding to the opacity measured to continually generate a rate-of-change signal to compare with the electrical signals characteristic of a leak in a bag of the baghouse bag system, and the processor may compare a rate-of-change signal with a predetermined rate of change value derived from empirical opacity measurements. The processor may be capable of determining the approximate location of a baghouse bag having a leak in a compartment using the time between start-up of the compartment and a change in opacity characteristic of a leak in a bag and the gas flow rate.
A baghouse filter system is disclosed comprising:                a) a housing comprising at least one compartment, each compartment comprising a first chamber and a second chamber, an inlet into the first chamber and an outlet from the second chamber, and a plurality of filter bags operatively positioned between the first and second chambers, the filter bags capable of filtering airborne particulate matter;        b) a blower operatively connected with the housing and capable of flowing air from the inlet through the filter bags and through the outlet;        c) a sensor positioned to measure opacity of gas flow from the outlet of the baghouse filter system; and        d) a processor capable of generating electrical signals corresponding to the opacity measured by the sensor and comparing the electrical signals corresponding to the opacity measured by the sensor with electrical signals characteristic of a leak in a bag of the baghouse bag system.        
The sensor may be positioned to measure opacity in an outlet of the baghouse system and may be capable of measuring light emitted by a light emitting diode to measure the opacity of gas flow. The processor may be capable of processing electrical signals before and during start-up of the baghouse system. Further, the processor may be capable of comparing the electrical signals corresponding to the opacity measured by the sensor with a reference electrical signal representing opacity measurements from the sensor during start-up of the baghouse system with a leak in a bag of the baghouse bag system to determine when a leak has occurred in a bag of the baghouse system.
These and other advantages and novel features, as well as details of illustrated embodiments thereof, will be more fully understood from the following description and drawings. Further disadvantages of conventional, traditional, and proposed embodiments will become apparent to one of skill in the art, from a description of embodiments of the system and method as set forth in the remainder of the present application with reference to the drawings.